This invention relates to a method and apparatus for the recovery of a suspension of fibrous material from mixed waste papers by first disintegrating the mixed papers into individual fibers, and then cleaning, floating and/or washing the separated fibers.
Waste paper consists of a mixture of many different types of paper. It includes, for instance, some paper which contains wood, other paper which is free of wood, unbleached kraft paper, cardboard, unbleached semi-chemical pulp and plastic-coated paper. Furthermore, the percentage of plastic-coated papers is increasing. Recovery of a suspension of fibrous material from this mixture of waste paper is difficult. Either a poor quality suspension is obtained or extensive and expensive paper treatment devices are necessary, which leads to high investment costs.
In German Provisional Patent (Auslegeschrift) No. 26 10 581, a method is described for obtaining relatively pure suspensions of fibrous material from waste paper, using a flotation device and a washing plant arranged one behind each other. If unbleached fibers, for instance, kraft papers and cardboards, are present, the fibers are also bleached in a bleaching tower. One disadvantage of this process and the plant for performing it is that it represents a considerable investment.